(1) Field of the Invention
This invention relates to an improvement in or relating spin drier to remove water droplets stuck on surfaces of semiconductor materials by centrifugal force and to dry same.
(2) Description of the Prior Art
This kind of spin drier comprises a casing and a rotor rotated in the casing, and the rotor has a plurality of air guides mounted on the base plate of the rotor. Semiconductor materials, usually called wafers, to be dried are housed in a carrier, the carrier being in turn housed in a cradle to be set in a predetermined area between the air guides in the rotor. There is provided a lid on the casing, which lid is positioned above the rotor and has a suction port formed therein. The casing has an exhaust port at a suitable position of its peripheral wall. Centrifugal force due to rotation of the rotor will scatter away and remove water droplets stuck on wafer surfaces, and wafers are dried by air stream introduced through the suction port due to negative air pressure in the central zone in the rotor, then the air stream flowing through wafers housed in the carrier along the peripheral wall of the casing and finally to the exhaust port.
In commonly accepted technique for supporting a carrier for wafers, for example as seen in FIGS. 10 and 11, while a cradle for housing a carrier has a port in its bottom wall through which air flows out, the carrier is housed in the cradle with a pair of carrier's legs engaging against both sides of the cradle bottom wall. This brings about the drawbacks mentioned below.
Since most of air passing through the carrier flows radially outward and thus perpendicularly to the cradle bottom wall, as seen in FIG. 11, a portion of the air flow impinges against the cradle bottom wall and splashes back, then flowing out, which results in vibrations and unstable behaviors on wafers in the carrier. Accordingly, this restricts the rotary speed of the rotor, and due to vibrations the carrier will suffer from minute cracks and being ground off at its groove-edges. Thus resulted minute particles will bring dusts which lead to a stain.